gnu: Add earlyoom-service-type.

* gnu/services/linux.scm: New file.
* tests/services/linux.scm: Add test.
* Makefile.am (SCM_TESTS): Register test.
* doc/guix.texi (Linux Services): Add a new section and document the new
service and its configuration.

Makefile.am

@@ -426,6 +426,7 @@ SCM_TESTS =					\
   tests/scripts-build.scm			\
   tests/search-paths.scm			\
   tests/services.scm				\
+  tests/services/linux.scm			\
   tests/sets.scm				\
   tests/size.scm				\
   tests/snix.scm				\

doc/guix.texi

@@ -48,7 +48,7 @@ Copyright @copyright{} 2017 humanitiesNerd@*
 Copyright @copyright{} 2017 Christopher Allan Webber@*
 Copyright @copyright{} 2017, 2018, 2019 Marius Bakke@*
 Copyright @copyright{} 2017, 2019 Hartmut Goebel@*
-Copyright @copyright{} 2017, 2019 Maxim Cournoyer@*
+Copyright @copyright{} 2017, 2019, 2020 Maxim Cournoyer@*
 Copyright @copyright{} 2017, 2018, 2019, 2020 Tobias Geerinckx-Rice@*
 Copyright @copyright{} 2017 George Clemmer@*
 Copyright @copyright{} 2017 Andy Wingo@*
@@ -310,6 +310,7 @@ Services
 * Version Control Services::    Providing remote access to Git repositories.
 * Game Services::               Game servers.
 * PAM Mount Service::           Service to mount volumes when logging in.
+* Linux Services::              Services tied to the Linux kernel.
 * Miscellaneous Services::      Other services.
 
 Defining Services
@@ -12084,6 +12085,7 @@ declaration.
 * Game Services::               Game servers.
 * PAM Mount Service::           Service to mount volumes when logging in.
 * Guix Services::               Services relating specifically to Guix.
+* Linux Services::              Services tied to the Linux kernel.
 * Miscellaneous Services::      Other services.
 @end menu
 
@@ -25129,6 +25131,71 @@ list.
 @end table
 @end deftp
 
+@node Linux Services
+@subsubheading Linux Services
+
+@cindex oom
+@cindex out of memory killer
+@cindex earlyoom
+@cindex early out of memory daemon
+@subsection Early OOM Service
+
+@uref{https://github.com/rfjakob/earlyoom,Early OOM}, also known as
+Earlyoom, is a minimalist out of memory (OOM) daemon that runs in user
+space and provides a more responsive and configurable alternative to the
+in-kernel OOM killer.  It is useful to prevent the system from becoming
+unresponsive when it runs out of memory.
+
+@deffn {Scheme Variable} earlyoom-service-type
+The service type for running @command{earlyoom}, the Early OOM daemon.
+Its value must be a @code{earlyoom-configuration} object, described
+below.  The service can be instantiated in its default configuration
+with:
+
+@lisp
+(service earlyoom-service-type)
+@end lisp
+@end deffn
+
+@deftp {Data Type} earlyoom-configuration
+This is the configuration record for the @code{earlyoom-service-type}.
+
+@table @asis
+@item @code{earlyoom} (default: @var{earlyoom})
+The Earlyoom package to use.
+
+@item @code{minimum-available-memory} (default: @code{10})
+The threshold for the minimum @emph{available} memory, in percentages.
+
+@item @code{minimum-free-swap} (default: @code{10})
+The threshold for the minimum free swap memory, in percentages.
+
+@item @code{prefer-regexp} (default: @code{#f})
+A regular expression (as a string) to match the names of the processes
+that should be preferably killed.
+
+@item @code{avoid-regexp} (default: @code{#f})
+A regular expression (as a string) to match the names of the processes
+that should @emph{not} be killed.
+
+@item @code{memory-report-interval} (default: @code{0})
+The interval in seconds at which a memory report is printed.  It is
+disabled by default.
+
+@item @code{ignore-positive-oom-score-adj?} (default: @code{#f})
+A boolean indicating whether the positive adjustments set in
+@file{/proc/*/oom_score_adj}.
+
+@item @code{show-debug-messages?} (default: @code{#f})
+A boolean indicating whether debug messages should be printed.  The logs
+are saved at @file{/var/log/earlyoom.log}.
+
+@item @code{send-notification-command} (default: @code{#f})
+This can be used to provide a custom command used for sending
+notifications.
+@end table
+@end deftp
+
 
 @node Miscellaneous Services
 @subsection Miscellaneous Services

gnu/services/linux.scm

@@ -0,0 +1,125 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu services linux)
+  #:use-module (guix gexp)
+  #:use-module (guix records)
+  #:use-module (guix modules)
+  #:use-module (gnu services)
+  #:use-module (gnu services shepherd)
+  #:use-module (gnu packages linux)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:use-module (ice-9 match)
+  #:export (earlyoom-configuration
+            earlyoom-configuration?
+            earlyoom-configuration-earlyoom
+            earlyoom-configuration-minimum-available-memory
+            earlyoom-configuration-minimum-free-swap
+            earlyoom-configuration-prefer-regexp
+            earlyoom-configuration-avoid-regexp
+            earlyoom-configuration-memory-report-interval
+            earlyoom-configuration-ignore-positive-oom-score-adj?
+            earlyoom-configuration-show-debug-messages?
+            earlyoom-configuration-send-notification-command
+            earlyoom-service-type))
+
+
+;;;
+;;; Early OOM daemon.
+;;;
+
+(define-record-type* <earlyoom-configuration>
+  earlyoom-configuration make-earlyoom-configuration
+  earlyoom-configuration?
+  (earlyoom earlyoom-configuration-earlyoom
+            (default earlyoom))
+  (minimum-available-memory earlyoom-configuration-minimum-available-memory
+                            (default 10)) ; in percent
+  (minimum-free-swap earlyoom-configuration-minimum-free-swap
+                     (default 10))      ; in percent
+  (prefer-regexp earlyoom-configuration-prefer-regexp ; <string>
+                 (default #f))
+  (avoid-regexp earlyoom-configuration-avoid-regexp  ; <string>
+                (default #f))
+  (memory-report-interval earlyoom-configuration-memory-report-interval
+                          (default 0)) ; in seconds; 0 means disabled
+  (ignore-positive-oom-score-adj?
+   earlyoom-configuration-ignore-positive-oom-score-adj? (default #f))
+  (run-with-higher-priority? earlyoom-configuration-run-with-higher-priority?
+                             (default #f))
+  (show-debug-messages? earlyoom-configuration-show-debug-messages?
+                        (default #f))
+  (send-notification-command
+   earlyoom-configuration-send-notification-command  ; <string>
+   (default #f)))
+
+(define (earlyoom-configuration->command-line-args config)
+  "Translate a <earlyoom-configuration> object to its command line arguments
+representation."
+  (match config
+    (($ <earlyoom-configuration> earlyoom minimum-available-memory
+                                 minimum-free-swap prefer-regexp avoid-regexp
+                                 memory-report-interval
+                                 ignore-positive-oom-score-adj?
+                                 run-with-higher-priority? show-debug-messages?
+                                 send-notification-command)
+     `(,(file-append earlyoom "/bin/earlyoom")
+       ,@(if minimum-available-memory
+             (list "-m" (format #f "~s" minimum-available-memory))
+             '())
+       ,@(if minimum-free-swap
+             (list "-s" (format #f "~s" minimum-free-swap))
+             '())
+       ,@(if prefer-regexp
+             (list "--prefer" prefer-regexp)
+             '())
+       ,@(if avoid-regexp
+             (list "--avoid" avoid-regexp)
+             '())
+       "-r" ,(format #f "~s" memory-report-interval)
+       ,@(if ignore-positive-oom-score-adj?
+             (list "-i")
+             '())
+       ,@(if run-with-higher-priority?
+             (list "-p")
+             '())
+       ,@(if show-debug-messages?
+             (list "-d")
+             '())
+       ,@(if send-notification-command
+             (list "-N" send-notification-command)
+             '())))))
+
+(define (earlyoom-shepherd-service config)
+  (shepherd-service
+   (documentation "Run the Early OOM daemon.")
+   (provision '(earlyoom))
+   (start #~(make-forkexec-constructor
+             '#$(earlyoom-configuration->command-line-args config)
+             #:log-file "/var/log/earlyoom.log"))
+   (stop #~(make-kill-destructor))))
+
+(define earlyoom-service-type
+  (service-type
+   (name 'earlyoom)
+   (default-value (earlyoom-configuration))
+   (extensions
+    (list (service-extension shepherd-root-service-type
+                             (compose list earlyoom-shepherd-service))))
+   (description "Run @command{earlyoom}, the Early OOM daemon.")))

tests/services/linux.scm

@@ -0,0 +1,57 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (tests services linux)
+  #:use-module (ice-9 match)
+  #:use-module (gnu packages linux)
+  #:use-module (gnu services linux)
+  #:use-module (guix gexp)
+  #:use-module (srfi srfi-64))
+
+;;; Tests for the (gnu services linux) module.
+
+(test-begin "linux-services")
+
+
+;;;
+;;; Early OOM daemon.
+;;;
+
+(define earlyoom-configuration->command-line-args
+  (@@ (gnu services linux) earlyoom-configuration->command-line-args))
+
+(define %earlyoom-configuration-sample
+  (earlyoom-configuration
+   (minimum-available-memory 10)
+   (minimum-free-swap 20)
+   (prefer-regexp "icecat")
+   (avoid-regexp "guix-daemon")
+   (memory-report-interval 60)
+   (ignore-positive-oom-score-adj? #f)
+   (run-with-higher-priority? #t)
+   (show-debug-messages? #f)
+   (send-notification-command "python \"/some/path/notify-all-users.py\"")))
+
+(test-equal "earlyoom-configuration->command-line-args"
+  (list (file-append earlyoom "/bin/earlyoom")
+        "-m" "10" "-s" "20" "--prefer" "icecat"
+        "--avoid" "guix-daemon" "-r" "60" "-p"
+        "-N" "python \"/some/path/notify-all-users.py\"")
+  (earlyoom-configuration->command-line-args %earlyoom-configuration-sample))
+
+(test-end "linux-services")